Image-forming apparatus and liquid-droplet-discharging method

Abstract

This image-forming apparatus includes a discharge unit and a control unit. On the basis of the distance between each nozzle part of a joint portion between two adjacent discharge heads among a plurality of discharge heads, the control unit controls the discharge of each nozzle part of the joint portion.

Description

Image forming apparatus and droplet ejection method

[0001] The present invention relates to an image forming apparatus and a droplet ejection method.

[0002] Conventionally, a configuration has been known that includes a head unit including multiple ejection heads capable of ejecting droplets. The head unit has multiple ejection heads arranged in a predetermined direction. The head unit moves multiple times in the predetermined direction, ejecting droplets onto a recording medium at each destination. By ejecting droplets multiple times in this manner, one line of an image is formed on the recording medium.

[0003] However, in a configuration having multiple ejection heads, droplets ejected from the nozzles corresponding to the joint between two adjacent ejection heads may overlap at the joint, resulting in image defects due to the overlapping droplets.

[0004] For example, Japanese Patent Application Laid-Open No. 2006-144992 discloses a configuration for preventing droplets from being ejected from nozzles corresponding to seams in order to prevent such image defects. By moving the head unit in a predetermined direction, another nozzle is positioned at a position corresponding to the area where droplets were not ejected, and droplets are then ejected.

[0005] Specifically, the head unit is set so that the position of the nozzles to be ejected becomes the position of the nozzles that are not to be ejected by moving the head unit. For example, the amount of movement of the head unit in one movement is set to about half the length of the ejection head, that is, the amount of movement of several nozzles lined up in a predetermined direction.

[0006] JP 2013-35160 A

[0007] However, the distance between the nozzles corresponding to the joints between the multiple ejection heads may differ from the spacing between the nozzles within the ejection head. Therefore, in a configuration in which the head unit is moved on a nozzle-by-nozzle basis, as in Patent Document 1, depending on the distance between the nozzles, when the head unit is moved, the positions of the nozzles that are to be ejected may not align with the positions of the nozzles that are not to be ejected, which may still result in poor image quality.

[0008] An object of the present invention is to provide an image forming apparatus and a droplet ejection method that can suppress image defects caused by nozzles at the joint between two adjacent ejection heads.

[0009] The image forming apparatus of the present invention comprises an ejection section, each having a plurality of nozzle sections arranged at equal intervals in a predetermined direction and including a plurality of ejection heads lined up in the predetermined direction, capable of moving in the predetermined direction to eject droplets onto a recording medium; and a control section that controls the ejection section so that the ejection section moves in the predetermined direction and ejects droplets at an interval narrower than the interval between two adjacent nozzle sections among the plurality of nozzle sections, and the control section controls the ejection of each nozzle section at the joint portion based on the distance between each nozzle section at the joint portion between two adjacent ejection heads among the plurality of ejection heads.

[0010] The droplet ejection method of the present invention is a droplet ejection method for an image forming device that includes a plurality of ejection heads that each have a plurality of nozzle portions arranged at equal intervals in a predetermined direction and are lined up in the predetermined direction, and that are equipped with ejection portions that can move in the predetermined direction to eject droplets onto a recording medium, and includes controlling the ejection portions so that they move in the predetermined direction at an interval narrower than the interval between two adjacent nozzle portions among the plurality of nozzle portions, and controlling the ejection portions includes controlling the ejection of each nozzle portion at the joint between two adjacent ejection heads among the plurality of ejection heads based on the distance between each nozzle portion at the joint.

[0011] According to the present invention, it is possible to suppress image defects caused by nozzles at the joint between two adjacent ejection heads.

[0012] FIG. 5A is a diagram schematically illustrating the overall configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 5B is a diagram illustrating the details of a head unit. FIG. 5C is a diagram illustrating image formation on a plurality of block regions. FIG. 5D is a diagram illustrating image formation on one block region. FIG. 5E is a diagram illustrating image formation when the distance between each nozzle section at a joint is shorter than the nozzle resolution. FIG. 5F is an enlarged view of an overlapping portion of droplets in FIG. 5A. FIG. 5G is a diagram illustrating image formation according to the control of the present invention. FIG. 6A is an enlarged view of an ejection point of the nozzle section at the joint. FIG. 6F is a diagram illustrating measurement of the distance between each nozzle section. FIG. 6G is a flowchart illustrating an example of the operation of image formation processing by a control section.

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described in detail with reference to the accompanying drawings. Fig. 1 is a diagram showing a schematic overall configuration of an image forming apparatus 1 according to an embodiment of the present invention.

[0014] 1, the image forming apparatus 1 is, for example, an inkjet type image forming apparatus, and includes a paper feed unit 11, a conveyance unit 12, an image forming unit 13, a fixing unit 14, a discharge unit 15, and a control unit 16.

[0015] The paper feed unit 11 supplies the recording medium P toward the conveyance unit 12. The conveyance unit 12 forms a conveyance path from when the recording medium P is supplied from the paper feed unit 11 through the image forming unit 13 and the fixing unit 14 until it is discharged to the discharge unit 15.

[0016] The recording medium P may be paper such as plain paper, high-quality paper, gloss coated paper, matte coated paper, synthetic paper, tack paper, colored paper, etc., film (including transparent and opaque films), cloth, etc. The recording medium P may also be a wiring board.

[0017] The image forming unit 13 has a head unit 131 that ejects ink (droplets) and is disposed at a distance from the transport path of the transport unit 12. The ink can be selected from known inks. For example, it may be an ultraviolet-curable liquid (photo-curable ink). Furthermore, the ink may be an insulating ink. For example, if the recording medium P is a wiring board, an insulating layer (solder resist) matching the wiring pattern of the wiring board is formed by applying insulating ink.

[0018] Four head units 131 are provided corresponding to the four color materials of Y, M, C, and K. The head units 131 correspond to the "discharge units" of the present invention. The head units 131 will be described in detail later.

[0019] The fixing unit 14 is disposed downstream in the conveying direction of the conveying unit 12 from the image forming unit 13. The fixing unit 14 irradiates activation energy such as ultraviolet light onto the recording medium P to cure and fix the ink ejected onto the recording medium P.

[0020] The discharge section 15 is a section where the recording medium P that has passed through the image forming section 13 and the fixing section 14 by the conveying section 12 is discharged.

[0021] The control unit 16 includes a CPU 16A (Central Processing Unit), a RAM 16B (Random Access Memory), a ROM 16C (Read Only Memory), a storage unit 16D, etc. The CPU 16A reads a program corresponding to the processing content from the ROM 16C, loads it into the RAM 16B, and centrally controls the operation of each block of the image forming apparatus 1 in cooperation with the loaded program. At this time, various data stored in the storage unit 16D is referenced. The storage unit 16D is configured, for example, with a non-volatile semiconductor memory (so-called flash memory) or a hard disk drive.

[0022] The control unit 16 controls the image forming unit 13 to form an image on the recording medium P. Specifically, the control unit 16 controls the ejection of droplets by each head unit 131 at each position to which the recording medium P is moved, while moving each head unit 131 multiple times in the main scanning direction.

[0023] 2, the head unit 131 has, for example, a plurality of ejection heads 132. Each of the plurality of ejection heads 132 has a plurality of nozzle portions 133 arranged at equal intervals in a predetermined direction (main scanning direction). The nozzle resolution of the ejection head 132 is a resolution corresponding to the interval between two adjacent nozzle portions 133 in the predetermined direction, and is, for example, 600 dpi. In other words, the interval between two adjacent nozzle portions 133 in the predetermined direction is a length corresponding to the distance between two adjacent dots in the predetermined direction of an image having a resolution equal to the nozzle resolution.

[0024] Each nozzle portion 133 has a plurality of holes in the transport direction of the recording medium P, which is perpendicular to the predetermined direction. Fig. 2 shows a nozzle portion 133 having four holes in the transport direction.

[0025] 2 shows only the first and second adjacent ejection heads 132A and 132B of the multiple ejection heads 132. The first ejection head 132A is located upstream of the second ejection head 132B in the movement direction of the head unit 131 during image formation (the direction toward the positive side of the predetermined direction).

[0026] The control unit 16 controls the head unit 131 to move in a predetermined direction and eject droplets at intervals narrower than the interval between two adjacent nozzle units 133 among the plurality of nozzle units 133. Specifically, for example, when forming an image based on image data with a resolution higher than the nozzle resolution, the control unit 16 controls the head unit 131 to move in units of the resolution of the high-resolution image data and eject droplets at each destination position on the recording medium P. In this case, as shown in FIG. 3 , the control unit 16 controls the head unit 131 to form images in sequence in each of a plurality of block areas lined up in a predetermined direction on the recording medium P.

[0027] More specifically, the control unit 16 first moves the head unit 131 in units of the image data resolution in the block area located at the most upstream side in the movement direction, and controls it so that droplets are ejected at each position in the block area.

[0028] For example, suppose the nozzle resolution of the ejection head 132 is 600 dpi and the resolution of the image data is 2400 dpi. In this case, within one block area, each of the multiple nozzle portions 133 ejects droplets at four locations, thereby completing an image within the block area.

[0029] 4, in the first droplet ejection, droplets are ejected from each nozzle portion 133 at the most upstream position in the block region. In the second droplet ejection, the head unit 131 moves from the droplet ejection position for the first time in units of the image data resolution, and droplets are ejected from each nozzle portion 133 at the destination position.

[0030] In the third droplet ejection, the head unit 131 moves from the second droplet ejection position in units of the image data resolution, and at the destination position, droplets are ejected from each nozzle portion 133. In the fourth droplet ejection, the head unit 131 moves from the third droplet ejection position in units of the image data resolution, and at the destination position, droplets are ejected from each nozzle portion 133.

[0031] 4, the distance between each nozzle portion 133 at the joint between a first ejection head 132A and a second ejection head 132B (described later) is equal to 600 dpi. Furthermore, in Figures 4 and subsequent figures, the portions indicated by circles are droplets that have landed on the recording medium P. Droplets ejected the first time are white circles, and droplets ejected the second time are black circles. Droplets ejected the third time are circles with a diagonal line inside, and droplets ejected the fourth time are circles with a dot inside.

[0032] In this way, when an image within the block area is formed, the control unit 16 moves the head unit 131 to a position corresponding to the block area adjacent to the block area, and controls it to eject droplets at each position in the block area.

[0033] In this way, images are formed in order in a plurality of block areas lined up in a predetermined direction, and when an image is formed in the block area located at the most downstream side in the direction of movement, an image of one line in the predetermined direction is formed. After that, an image is similarly formed in the line adjacent to the image of that one line in the transport direction.

[0034] Depending on the distance between the nozzle portions 133 at the joint between the first ejection head 132A and the second ejection head 132B, droplets ejected from the nozzle portions 133 corresponding to the joint may overlap on the recording medium P.

[0035] For example, suppose the distance between the nozzle portions 133 at the seam is shorter than the nozzle resolution (e.g., 600 dpi). In such a case, when forming an image with a higher resolution than the nozzle resolution, there is a possibility that the droplets ejected from the nozzle portions 133 corresponding to the seams of the first ejection head 132A and the second ejection head 132B will overlap each other when ejecting droplets for the second or subsequent times.

[0036] For example, when forming an image at 2400 dpi, as described above, droplets are ejected a total of four times from each nozzle portion 133. In this case, during the second or subsequent droplet ejection, there is a possibility that droplets ejected from the nozzle portion 133 at the joint of the first ejection head 132A may overlap with droplets ejected from the nozzle portion 133 at the joint of the second ejection head 132B during at least the first droplet ejection.

[0037] 5A shows an example in which droplets ejected from the nozzle portion 133 at the joint of the first ejection head 132A during the third ejection of droplets overlap at point S with droplets ejected from the nozzle portion 133 at the joint of the second ejection head 132B during the first ejection of droplets. Fig. 5B shows an example in which point S is enlarged. D1 is a droplet ejected from the first ejection head 132A during the third ejection. D2 is a droplet ejected from the second ejection head 132B during the first ejection.

[0038] In this embodiment, the control unit 16 controls the ejection of each nozzle portion 133 at the joint portion between adjacent first ejection head 132A and second ejection head 132B among the multiple ejection heads 132 based on the distance between each nozzle portion 133 at the joint portion.

[0039] The control unit 16 controls the ejection by the first nozzle unit 133A at the ejection location of the first nozzle unit 133A and the ejection by the second nozzle unit 133B at the ejection location of the second nozzle unit 133B. The first nozzle unit 133A is the nozzle unit 133 corresponding to the joint portion of the first ejection head 132A. The second nozzle unit 133B is the nozzle unit 133 corresponding to the joint portion of the second ejection head 132B.

[0040] Specifically, the control unit 16 adjusts the ratio of ejection by the first nozzle unit 133A and ejection by the second nozzle unit 133B at locations corresponding to the ejection locations of the first nozzle unit 133A and the second nozzle unit 133B on the recording medium P. For example, the control unit 16 controls the first nozzle unit 133A to eject droplets and the second nozzle unit 133B not to eject droplets at locations where the droplets from the first nozzle unit 133A and the droplets from the second nozzle unit 133B overlap.

[0041] For example, in the example shown in Figure 5A, the location corresponding to the position of the second ejection head 132B during the first and second ejections is the same as the location corresponding to the position of the first ejection head 132A during the third and fourth ejections.

[0042] 6A and 6B, the control unit 16 controls the second nozzle portion 133B of the second ejection head 132B not to eject droplets during the first and second ejections. The square marked with 133A in Fig. 6A indicates the position of the first nozzle portion 133A of the first ejection head 132A. The square marked with 133B indicates the position of the second nozzle portion 133B of the second ejection head 132B.

[0043] Since no droplets are ejected from the second nozzle portion 133B during the first and second ejections, the area corresponding to the second nozzle portion 133B is shown by a dashed line in Figures 6A and 6B.

[0044] Then, the control unit 16 controls the first nozzle unit 133A of the first ejection head 132A to eject droplets from the first nozzle unit 133A during the third and fourth ejections. In Fig. 6B, the first nozzle unit 133A moves to the dashed line location adjacent to the droplet ejected by the first nozzle unit 133A during the second ejection, and the third ejection is performed. Also, in Fig. 6B, the first nozzle unit 133A moves to the dashed line location adjacent to the droplet ejected by the first nozzle unit 133A during the third ejection, and the fourth ejection is performed.

[0045] This makes it possible to prevent overlapping of droplets ejected from the nozzle portions 133 corresponding to the joint between the first ejection head 132A and the second ejection head 132B, which means that image defects caused by the nozzle portions 133 at the joint between two adjacent ejection heads 132 can be prevented.

[0046] The control unit 16 may perform control to measure the distance between the nozzle portions 133 at the joint between the two ejection heads 132 .

[0047] For example, the control unit 16 may perform control to measure the distance between each nozzle unit 133 before forming an image on the recording medium P. Before forming an image on the recording medium P may be, for example, when the image forming apparatus 1 starts to be used, or may be after receiving a command for a print job but before the print job is executed.

[0048] The control for measuring the distance between the nozzle portions 133 at the joint portion may be control for forming a predetermined pattern on the recording medium P. The predetermined pattern may be, for example, a rectangular pattern formed by each of the multiple ejection heads 132.

[0049] For example, if the resolution of the image data for a print job is greater than the nozzle resolution, and the distance between the nozzle sections 133 at the joint is shorter than the nozzle resolution, when rectangular images are formed by the first ejection head 132A and the second ejection head 132B, adjacent portions of the two rectangles will overlap.

[0050] 7 shows a rectangle R1 formed by the first ejection head 132A and a rectangle R2 formed by the second ejection head 132B. By measuring the length of R3, which is the overlapping portion between the rectangles R1 and R2, it is possible to measure the distance between the nozzle portions 133.

[0051] The distance between each nozzle portion 133 may be measured based on read information obtained by reading an image of a predetermined pattern using a reading device or the like, or may be measured by the user visually inspecting the recording medium P on which the image is formed.

[0052] Then, based on the distance information obtained by the above measurement, the control unit 16 controls whether or not to eject from the nozzle portion 133 at the joint portion. In this way, it becomes possible to easily measure the distance between the nozzle portions 133.

[0053] The distance between the nozzle portions 133 corresponding to the joints may be determined based on information measured in advance for each image resolution.

[0054] Next, the flow of image formation control by the control unit 16 will be described. Fig. 8 is a flowchart showing an example of the operation of image formation processing by the control unit 16. This control is started when an execution command for a print job is acquired. Note that the flowchart in Fig. 8 is based on the premise that the resolution of the image data is higher than the nozzle resolution.

[0055] 8, the control unit 16 determines whether the distance between the nozzle portions 133 at the joint between the first ejection head 132A and the second ejection head 132B is smaller than the distance corresponding to the nozzle resolution (step S101). If the determination result shows that the distance between the nozzle portions 133 is equal to or greater than the distance corresponding to the nozzle resolution (step S101, NO), the control unit 16 executes normal control (step S102). The normal control may be, for example, control in which droplets are ejected from all of the nozzle portions 133.

[0056] If the distance between the nozzle portions 133 at the joints is greater than the distance of the nozzle resolution, for example, when droplets are ejected four times on a 2400 dpi image, a gap will be created between the images of the first ejection head 132A and the second ejection head 132B. In this case, the control unit 16 can move the head unit 131 in units of resolution and control the head unit 131 so that droplets are ejected only at locations corresponding to the gaps.

[0057] On the other hand, if the distance between the nozzle portions 133 is smaller than the distance of the nozzle resolution (step S101, YES), the control unit 16 controls the ejection of the nozzle portions 133 at the joint (step S103).

[0058] After step S102 or step S103, this control ends.

[0059] According to the present embodiment configured as described above, ejection from each nozzle portion 133 at the joint between two adjacent ejection heads 132 is controlled based on the distance between each nozzle portion 133 corresponding to the joint.

[0060] The distance between each nozzle portion 133 corresponding to the seam may deviate from the ideal value due to manufacturing errors or deterioration over time, so for example, when forming an image with a higher resolution than the nozzle resolution, there is a possibility that droplets ejected from each nozzle portion 133 may overlap.

[0061] In this embodiment, droplets are ejected from either the first nozzle portion 133A or the second nozzle portion 133B at locations corresponding to the ejection locations of the first nozzle portion 133A and the second nozzle portion 133B on the recording medium P. Then, control is performed so that droplets are not ejected from the other of the first nozzle portion 133A and the second nozzle portion 133B.

[0062] This makes it possible to prevent overlapping of droplets ejected from the nozzle portions 133 corresponding to the joint between the first ejection head 132A and the second ejection head 132B, which means that image defects caused by the nozzle portions 133 at the joint between two adjacent ejection heads 132 can be prevented.

[0063] Furthermore, when the recording medium P is a wiring substrate, it is necessary to precisely control the thickness of the droplets (insulating layer). In this embodiment, overlapping of droplets is suppressed, so that even when the recording medium P is a wiring substrate, the thickness of the droplets can be precisely controlled.

[0064] In the above embodiment, at a location where the droplets from the first nozzle portion 133A and the second nozzle portion 133B overlap, the droplets are ejected from the first nozzle portion 133A, but not from the second nozzle portion 133B. However, the present invention is not limited to this, and at the overlapping location, the droplets may be ejected from the second nozzle portion 133B, but not from the first nozzle portion 133A.

[0065] Furthermore, the control unit 16 may cause droplets to be ejected from some of the multiple holes of the first nozzle unit 133A, and may prevent droplets from being ejected from the other multiple holes of the first nozzle unit 133A. In this case, the control unit 16 may cause droplets to be ejected from holes of the multiple holes of the second nozzle unit 133B that are located at positions different from some of the multiple holes of the first nozzle unit 133A, and may prevent droplets from being ejected from holes other than the holes.

[0066] That is, the control unit 16 may adjust the usage rate of the multiple holes of the first nozzle unit 133A and the usage rate of the multiple holes of the second nozzle unit 133B at a location where the droplets from the first nozzle unit 133A and the droplets from the second nozzle unit 133B overlap. Furthermore, the usage rate of the multiple holes of the first nozzle unit 133A and the usage rate of the multiple holes of the second nozzle unit 133B may be any value as long as the sum of both is 100%.

[0067] Furthermore, the above-described embodiments are merely examples of specific embodiments for carrying out the present invention, and the technical scope of the present invention should not be construed as being limited by these embodiments. In other words, the present invention can be carried out in various forms without departing from the gist or main features thereof.

[0068] The disclosures of the specification, drawings and abstract contained in Japanese Patent Application No. 2024-122338, filed on July 29, 2024, are incorporated herein by reference in their entirety.

[0069] REFERENCE SIGNS LIST 1 image forming apparatus 11 paper feed section 12 transport section 13 image forming section 14 fixing section 15 discharge section 16 control section 131 head unit 132 ejection head 132A first ejection head 132B second ejection head 133 nozzle section 133A first nozzle section 133B second nozzle section

Claims

1. An image forming device comprising: a discharge unit that has a plurality of nozzle units arranged at equal intervals in a predetermined direction and includes a plurality of discharge heads lined up in the predetermined direction, and that is capable of moving in the predetermined direction to discharge droplets onto a recording medium; and a control unit that controls the discharge unit so that it moves in the predetermined direction and discharges droplets at intervals narrower than the interval between two adjacent nozzle units among the plurality of nozzle units, wherein the control unit controls the discharge of each nozzle unit at the joint between two adjacent discharge heads among the plurality of discharge heads based on the distance between each nozzle unit at the joint.

2. The image forming apparatus according to claim 1, wherein the control unit controls the ejection of a first nozzle portion corresponding to the joint portion of one of the two ejection heads and a second nozzle portion corresponding to the joint portion of the other of the two ejection heads.

3. The image forming apparatus according to claim 2, wherein the control unit adjusts the ratio of ejection by the first nozzle unit and ejection by the second nozzle unit at locations on the recording medium corresponding to ejection locations of the first nozzle unit and ejection locations of the second nozzle unit.

4. The image forming apparatus according to claim 3, wherein the control unit controls so that droplets are ejected from either the first nozzle unit or the second nozzle unit at the location, and so that droplets are not ejected from the other of the first nozzle unit and the second nozzle unit.

5. The image forming apparatus according to claim 1, wherein the control unit controls the ejection unit so as to form images in order on each of a plurality of block areas aligned in the predetermined direction on the recording medium.

6. The image forming device according to claim 1, wherein when forming an image with a resolution higher than the resolution corresponding to the spacing between two adjacent nozzle sections among the plurality of nozzle sections, the control section controls the ejection section to move in the specified direction and eject droplets in units of the resolution of the high resolution.

7. The image forming apparatus according to claim 1, wherein the recording medium is a wiring board.

8. The image forming apparatus according to claim 7, wherein the droplets are photocurable ink.

9. The image forming apparatus according to claim 8, wherein the droplets are insulating ink.

10. A droplet ejection method for an image forming device including a plurality of ejection heads each having a plurality of nozzle sections arranged at equal intervals in a predetermined direction and aligned in the predetermined direction, and having an ejection section capable of moving in the predetermined direction to eject droplets onto a recording medium, the method comprising controlling the ejection section so that the ejection section moves in the predetermined direction to eject droplets at an interval narrower than the interval between two adjacent nozzle sections among the plurality of nozzle sections, and controlling the ejection section comprises controlling the ejection of each nozzle section at a joint between two adjacent ejection heads among the plurality of ejection heads based on the distance between each nozzle section at the joint.

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